CSE240 (online) Lecture 12

Introduction to Programming Languages
Programming with LISP
(201805)

Transcript

1. CSE240 – Introduction to Programming Languages (online) Lecture 12: Programming with LISP Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu Office Hours: By appointment
2. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 2 Functional Programming • Language: we will use LISP (LISt Processing). • It uses an interpreter. • Automatic management of memory. • More abstract than Imperative and Object-Oriented: no data types and a simpler syntax.
3. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 3 You need an Interpreter • LispWork Personal Edition – http://www.lispworks.com/downloads/index.html • Compile Lisp Online – http://rextester.com/l/common_lisp_online_compiler • Steel Bank Common Lisp – http://www.sbcl.org/platform-table.html
4. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 4 Functional Programming • A program is a set of lists and they are enclosed with parenthesis. • We use lists to represent functions; in a function the first element of the list is the id of the function and the rest are parameter(s) • Whitespace separate function id and parameters • Examples: ( print "Hello World" ) ( + 2 2 ) ( sqrt 2 )
5. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 5 Everything is a List • Uniform representation of instructions and data using a single general format– a list. (functionId param1 param2 param3 ...) • (+ 3 2 7 9) ; add 3+2+7+9 and return the result 21 • (* 4 2.3) ; multiply 4 by 2.3 and return the result 9.2 • (subseq "Hello, World" 2 9) "llo, Wo"
6. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 6 Important Notice !
7. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 7 Everything is a List • A function ID (symbol) is a series of characters other than whitespace, parentheses ( ), pound ( # ), quote ( ' ), double-quote ( " ), period ( . ), or back quote ( ` ). • A function ID (symbol) may not take the form of numbers. • It's very common for symbols to have hyphens ( - ) or asterisks ( * ) in them. • There are NOT operators! only functions • Symbols (function ID) are case-INSENSITIVE.
8. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 8 Atomic Expressions • -3 • 2.43 • 123342303923412323411323234012923492341231230234923410239234412 • #C(3.2 2) ; the complex number 3.2 + 2i • 2/3 ; the fraction 2/3. It is NOT divide 2 by 3 • -3.2e25 ; the number -3.2 x 10^25 • #\g ; characters starts with #\ • #\{ • #\\ ; the character '\' • #\tab
 • #\newline • 
#\space
 • #\backspace
 • #\escape
9. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 9 Atomic Expressions • "Hello, World!" • "It's a glorious day." • "He said \"No Way!\" and then he left." • "I think I need a backslash here: \\ Ah, that was better." • t ; true • nil ; false
10. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 10 Everything is a List • (+ 27/32 32/57) 2563/1824 • (* 2.342 3.2e4) 74944.0 • (* 2.342 9.212 -9.23 3/4) ; You can mix number types -149.34949 • (/ 3 5) ; The return type stays as general as possible 3/5 • (/ 3.0 5) ;Here LISP had no choice: convert to a float 0.6 • (1+ 3) 4
11. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 11 Everything is a List • (string-upcase "How about that!") "HOW ABOUT THAT!" • (reverse "Four score and seven years ago") "oga sraey neves dna erocs ruoF" • (length "Four score and seven years ago") 30 • (sqrt 2) 1.4142135 • (sqrt -1.0) #C(0 1.0) • (SqRt -1.0) ;LISP symbols are case-insensitive #C(0 1.0)
12. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 12 Function Arguments • Some functions have NOT a fixed number of arguments: (+ 100 231 201 921 221 231 -23 12 -34 134) • Some functions have a fixed number of arguments and optional arguments: (subseq "Four score and seven years ago" 9) "e and seven years ago” (subseq "Four score and seven years ago" 9 23) "e and seven ye"
13. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 13 Predicates (boolean functions) • LISP has a special name for functions which return "true" (usually t) or "false" (nil). These functions are called predicates. • (= 4 3) ; is 4 == 3 ? NIL • (< 3 9) ; is 3 < 9 ? T • (numberp "hello") ; is "foo" a number? NIL • (oddp 9) ; is 9 an odd number? T
14. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 14 Errors • Errors stop the program execution • (/ 1 0) *** - division by zero • (blah-blah-blah 1 0 "foo") *** - EVAL: the function BLAH-BLAH-BLAH is undefined
15. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 15 Recursion • When a list contains another list among its expressions, the evaluation procedure is recursive. • (+ 33 (* 2.3 4) 9) 51.2 • (+ (length "Hello World") 44) 55 • (* (+ 3 2.3) (/ 3 (- 9 4))) ;in C++: (3+2.3) * (3 / (9-4)) 3.1800003 • (log (log (log 234231232234234123))) 1.3052895 • (+ (* (sin 0.3) (sin 0.3)) ; expressions may use multiple lines (* (cos 0.3) (cos 0.3))) ; sin(0.3)^2 + cos(0.3)^2 1.0000001 ; = 1. Rounding inaccuracy
16. Javier Gonzalez-Sanchez | CSE 240 (online) | Fall 2017 | 16 Recursion • (and (< 3 (* 2 5)) (not (>= 2 6))) ; (3 < 2 * 5) && !(2 >= 6) T • (print (+ 2 3 4 1)) 10 10 • (+ (* 2 3) (/ 3 2) 9) 33/2
17. CSE240 – Introduction to Programming Languages (online) Javier Gonzalez-Sanchez javiergs@asu.edu Fall 2017 Disclaimer. These slides can only be used as study material for the class CSE240 at ASU. They cannot be distributed or used for another purpose.